Combustor and gas turbine

ABSTRACT

A combustor of the present disclosure includes: a mixing portion which is provided with a plurality of mixing passages passing through the mixing portion so as to be extended from an upstream end surface to a downstream end surface of the mixing portion intersecting an axis of the combustor, air being introduced to the plurality of the mixing passages from the upstream end surface of the mixing portion; and a fuel supply portion which is configured to supply the air introduced to the mixing passages with fuel to generate mixed fluid, wherein flow paths of the mixing passages have different pressure loss coefficients so that the differences in the flow velocity of the mixed fluid flowing through the mixing passages at the downstream end surface of the mixing portion are greater than those of a case where the mixing passages have the same flow path shape.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a combustor and a gas turbine.

Priority is claimed on Japanese Patent Application No. 2022–36060. filed Mar. 9, 2022, the content of which is incorporated herein by reference.

Description of Related Art

For example, Japanese Unexamined Patent Publication No. 2013-234834 discloses a cluster combustor as an example of a combustor used in a gas turbine.

The cluster combustor includes a plurality of mixing passages which are arranged side by side and into which air is introduced and a fuel supply portion which injects a fuel from inner peripheral surfaces of these mixing passages. A mixed fluid of the air and the fuel flows through the mixing passage and is ejected downstream as the fuel is injected. At this time, the mixed fluid is ignited to form a plurality of small-scale flames at an outlet of each mixing passage.

In the above-described cluster combustor, the inlet portions of the mixing passages have different shapes in order to improve the non-uniformity of the flow rate of air introduced into the mixing passages. That is, more air is allowed to flow into the mixing passage by enlarging the inlet portion of the mixing passage into which the air flow rate is small. Accordingly, the flow rate of air in each mixing passage is made uniform, and the flow velocity of the mixed fluid at the outlet of the mixing passage is made uniform.

SUMMARY OF THE INVENTION

Incidentally, in the combustor disclosed in JP 2013-234834, the positions of the flame surfaces formed by the continuous flames at the outlets of the mixing passages are aligned in the axial direction of the combustor, and combustion oscillation may occur.

The present disclosure has been made to solve the above-described problems and an object thereof is to provide a combustor and a gas turbine capable of suppressing vibration.

In order to solve the above-described problems, a combustor according to the present disclosure includes: a mixing portion which is provided with a plurality of mixing passages passing through the mixing portion so as to be extended from an upstream end surface to a downstream end surface of the mixing portion intersecting an axis of the combustor, air being introduced to the plurality of the mixing passages from the upstream end surface of the mixing portion; and a fuel supply portion which is configured to supply the air introduced to the mixing passages with fuel to generate mixed fluid, wherein flow paths of the mixing passages have different pressure loss coefficients so that the differences in the flow velocity of the mixed fluid flowing through the mixing passages at the downstream end surface of the mixing portion are greater than those of a case where the mixing passages have the same flow path shape.

A gas turbine according to the present disclosure includes: a compressor which generates air; the combustor generating a combustion gas by mixing a fuel with air compressed by the compressor and combusting the generated mixed fluid: and a turbine being driven by the combustion gas.

According to the combustor and the gas turbine of the present disclosure, vibration can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a schematic configuration of a gas turbine according to a first embodiment of the present disclosure.

FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a combustor according to the first embodiment of the present disclosure,

FIG. 3 is a view of a mixing portion of the combustor according to the first embodiment of the present disclosure when viewed from a combustor axial direction.

FIG. 4 is an enlarged view of a main part of the combustor according to the first embodiment of the present disclosure,

FIG. 5 is a diagram showing a flow velocity distribution of air and mixed fluid and a distribution of a flame surface of a combustor of a comparative example.

FIG. 6 is a diagram showing a flow velocity distribution of air and mixed fluid and a distribution of a flame surface of the combustor according to the first embodiment of the present disclosure.

FIG. 7 is a vertical cross-sectional view showing a schematic configuration of a combustor according to a second embodiment of the present disclosure.

FIG. 8 is an enlarged view of a main part of the combustor according to the second embodiment of the present disclosure.

FIG. 9 is an enlarged view of a main part of a combustor according to a modified example.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6 .

As shown in FIG. 1 , a gas turbine 1 according to this embodiment includes a compressor 2 which compresses air, a combustor 3 which generates a combustion gas, and a turbine 4 which is driven by the combustion gas. The plurality of combustors 3 are provided around a rotating shaft of the gas turbine 1 at intervals in the circumferential direction. The combustor 3 mixes and combusts the air compressed by the compressor 2 with fuel to generate a high-temperature and high-pressure combustion gas.

Combustor

Hereinafter, the configuration of the combustor 3 will be described with reference to FIGS. 2 to 4 .

As shown in FIG. 2 , the combustor 3 includes an outer cylinder 10, an end cover 11, an inner cylinder 13, a mixing portion 20. a support portion 38, and a fuel nozzle 40 which is an example of a fuel supply portion.

Outer Cylinder

A cylinder body has a cylindrical shape centered on a combustor axis O (hereinafter, simply referred to as axis O) that is the center of the combustor 3.

End Cover

An end cover has a disc shape that closes an end portion on one side of the outer cylinder 10 in the direction of the axis O (the left side in FIG. 2 ). The end portion on one side of the outer cylinder 10 in the direction of the axis O comes into contact with the end cover 11. A fuel header 12 which is a space is formed inside the end cover 11. A fuel F is supplied to the fuel header 12 from the outside. As the fuel F. for example, a mixed fuel of a natural gas and hydrogen may be used.

Inner Cylinder

The inner cylinder 13 is coaxially disposed inside the outer cylinder 10. The inner cylinder 13 has a cylindrical shape extending in the direction of the axis O inside the outer cylinder 10. An end portion of the inner cylinder 13 on one side in the direction of the axis O is separated from the end cover 11 in the direction of the axis O. The outer diameter of the inner cylinder 13 is smaller than the outer diameter of the inner cylinder 13. Accordingly, an annular flow path is formed between the outer peripheral surface of the inner cylinder 13 and the inner peripheral surface of the outer cylinder 10. Air A compressed by the compressor 2 flows through the flow path from the other side in the direction of the axis O (the right side in FIG. 2 ) to one side in the direction of the axis O.

Mixing Portion

The mixing portion 20 has a columnar shape centered on the axis O and includes an upstream end surface 21 and a downstream end surface 22. The mixing portion 20 is provided to be coaxially fitted inside the inner cylinder 13.

The upstream end surface 21 is an end surface which faces one side of the mixing portion 20 in the direction of the axis O and has a planar shape orthogonal to the axis O. The upstream end surface 21 is disposed at the same position in the direction of the axis O as the end surface on one side of the inner cylinder 13 in the direction of the axis O.

The downstream end surface 22 is an end surface which faces the other side of the mixing portion 20 in the direction of the axis O and has a planar shape orthogonal to the axis O. The downstream end surface 22 is located on one side in the direction of the axis O relative to the end surface of the inner cylinder 13 on the other side in the direction of the axis O. Accordingly, a space is defined by the inner peripheral surface of the inner cylinder 13 and the downstream end surface 22 of the mixing portion 20. The space is formed as a combustion space of the combustor 3.

The mixing portion 20 is provided with a plurality of mixing passages 30 which extend in the direction of the axis O to penetrate the upstream end surface 21 and the downstream end surface 22. The inside of the mixing passage 30 is a flow path in which one side in the direction of the axis O is the upstream side and the other side of the axis O is the downstream side.

Here, as shown in FIG. 3 , a plurality of mixing passage groups in which the plurality of mixing passages 30 are bundled are formed in the mixing portion 20, In this embodiment, a first group B1 and a second group B2 are formed as the mixing passage group.

The first group B1 is a mixing passage group which is collectively disposed in a center region of the downstream end surface 22, that is, an annular region centered on the axis O.

The second group B2 is a mixing passage group which is collectively disposed on the outer peripheral side of the first group B1 and is formed at a plurality of positions at intervals in the circumferential direction. The mixing passage 30 constituting the second group B2 is divided into an inner peripheral system R1 and an outer peripheral system R2. The inner peripheral system R1 is formed from the plurality of mixing passages 30 collectively arranged in the center of each second group B2. The outer peripheral system R2 is formed from the plurality of mixing passages 30 collectively arranged to surround the inner peripheral system R1 in each second group B2 from the outer peripheral side.

Fuel Nozzle

As shown in FIG. 2 , the fuel nozzle 40 has a tubular shape extending in the direction of the axis O and has a role of injecting the fuel F into the mixing passage 30. The plurality of fuel nozzles 40 are provided in a one-to-one relationship with the mixing passages 30 to correspond to the respective mixing passages 30. A portion of the fuel nozzle 40 on one side in the direction of the axis O is fixed to the end cover 11. The fuel nozzle 40 is provided across the end cover 11 and the mixing passage 30.

The end portion of the fuel nozzle 40 on one side in the direction of the axis O is connected to the fuel header 12 inside the end cover 11. Accordingly, the fuel header 12 and the fuel nozzle 40 are in communication with each other and the fuel F in the fuel header 12 is supplied to the fuel nozzle 40.

The end portion of the fuel nozzle 40 on the other side in the direction of the axis O is inserted into the mixing passage 30. Accordingly, the fuel F flowing through the fuel nozzle 40 is injected from the end portion of the fuel nozzle 40 on the other side in the direction of the axis O.

Support Portion

The support portion 38 supports the mixing portion 20 on the end cover 11. The end portion of the support portion 38 on one side in the direction of the axis O is fixed to the end cover 11 and the end portion on the other side is connected to the outer peripheral portion of the upstream end surface 21 of the mixing portion 20. The plurality of support portions 38 are formed at intervals in the circumferential direction. The air A flowing through the flow path between the inner peripheral surface of the outer cylinder 10 and the outer peripheral surface of the inner cylinder 13 from the other side to one side in the direction of the axis O is reversed to the other side in the direction of the axis O to pass through a space between the plurality of support portions 38.

Detailed Configuration of Mixing Passage and Fuel Nozzles

Next, the detailed configuration of the mixing passage 30 and the fuel nozzle 40 will be described with reference to FIG. 4 .

Each mixing passage 30 includes a main portion 31 and an inlet portion 32. The main portion 3 has a uniform inner diameter and extends straight in the direction of the axis O, and the end portion on the downstream side (the right side in FIG. 4 ) opens to the downstream end surface 22 as an outlet opening 31 a. The inlet portion 32 is continuous to the upstream side (the left side in FIG. 4 ) of the main portion 31 and extends further upstream, and the upstream end portion opens to the upstream end surface 21 as an inlet opening 32 a.

The inlet portion 32 has a bell mouth shape which increases in inner diameter toward the upstream side and is continuous to the upstream end surface 21. The length of the inlet portion 32 in the direction of the axis O of the mixing passage 30 is shorter than the length of the main portion 31 in the direction of the axis O.

In the fuel nozzle 40, a tip 41 which is a portion on the other side in the direction of the axis O is inserted from the inlet opening 32 a of the mixing passage 30. The tip 41 of the fuel nozzle 40 is provided with a tip opening 42 a which injects the fuel F flowing through a fuel flow path 42 inside the fuel nozzle 40. The tip opening 42 a is located on the downstream side in relation to the boundary between the main portion 31 and the inlet portion 32. A nozzle outer peripheral surface 43 which is the outer peripheral surface of the tip 41 of the fuel nozzle 40 decreases in diameter toward the tip side. The outer diameter of the nozzle outer peripheral surface 43 is smaller than the inner diameter of the inlet portion 32 of the mixing passage 30. The center axis of the fuel nozzle 40 matches the center axis of the mixing passage 30. Accordingly, the flow path of the air A flowing into the mixing passage 30 is formed by the nozzle outer peripheral surface 43 and the inner peripheral surface of the inlet portion 32 of the mixing passage 30.

In this embodiment, as shown in FIG. 4 , when any two mixing passages 30 are a first mixing passage 30A and a second mixing passage 30B, the inlet portions 32 of the first mixing passage 30A and the second mixing passage 30B have different flow path shapes.

That is, in this embodiment, the first mixing passage 30A and the second mixing passage 30B have the same shape. On the other hand, the outer diameter of the nozzle outer peripheral surface 43 of the fuel nozzle 40 inserted into the first mixing passage 30A is smaller than the outer diameter of the nozzle outer peripheral surface 43 of the fuel nozzle 40 inserted into the second mixing passage 30B. Accordingly, the flow path shape formed by the nozzle outer peripheral surface 43 and the inner peripheral surface of the inlet portion 32 is narrower in the second mixing passage 30B than in the first mixing passage 30A.

That is, the size of the flow path cross-section of the inlet portion 32 is smaller in the second mixing passage 30B than in the first mixing passage 30A. The effective cross-sectional area through which the air A can flow is smaller at the inlet portion 32 of the second mixing passage 30B than at the inlet portion 32 of the first mixing passage 30A. As a result, the pressure loss coefficient of the second mixing passage 30B becomes smaller than the pressure loss coefficient of the first mixing passage 30A.

In this way, in this embodiment, at least one pair of mixing passages 30 are configured such that the pressure loss coefficients of the flow paths are different from each other.

Here, in this embodiment, the fuel supply rate from the fuel nozzle 40 to the first mixing passage 30A is larger than the fuel supply rate to the second mixing passage 30B. That is, the fuel supply nozzles 40 and the mixing passages 30 are combined such that the lower the pressure loss coefficient of the mixing passage 30. the higher the fuel supply rate of the fuel supply nozzle 40. Such adjustment of the fuel supply rate can be performed by installing an orifice inside the fuel header 12 or appropriately setting the shape of the fuel flow path 42 and the like. Accordingly, the fuel-air ratio of each mixing passage 30 can be made uniform, and stable combustion can be performed.

Operation and Effect

Next, the operation and effect of the combustor 3 according to this embodiment will be described.

During the operation of the gas turbine 1. the fuel F is injected from each fuel nozzle 40 while the air A flows through each mixing passage 30. The fuel F injected into the mixing passage 30 is mixed with the air A flowing through the mixing passage 30 to thereby generate a mixed fluid M. The mixed fluid M is ejected downstream from the downstream end surface 22 of the mixing portion 20 through the outlet opening 31 a of the mixing passage 30 and is ignited. Accordingly, a flame is formed to correspond to the outlet opening 31 a of each mixing passage 30 and the generated combustion gas C is sent to the turbine 4.

Here, when it is assumed that the flow path shapes of the mixing passages 30 are the same among the mixing passages 30, the inlet side flow velocity distribution D1 which is the flow velocity distribution of the air A on the upstream side of each mix ing passage 30 and the outlet side flow velocity distribution D2 on the downstream side of the mixing passage 30 are the same as shown in the comparative example of FIG. 5 . In this case, when the variation in the inlet side flow velocity distribution D1 is small, the outlet side flow velocity distribution D2 also has less variation and becomes uniform. As a result, the flame surface S formed by the flame from each mixing passage 30 is aligned in the direction of the axis O and combustion oscillation occurs.

On the other hand, in this embodiment, the above problem is solved by making the pressure loss coefficients of the mixing passages 30 different from each other.

That is, in this embodiment, as shown in FIG. 4 , since the first mixing passage 30A and the second mixing passage 30B have different inlet side flow path shapes, the pressure loss coefficients are different from each other. More specifically, the pressure loss coefficient is large in the second mixing passage 30B having a narrow inlet side flow path shape compared to the first mixing passage 30A.

Here, when a pressure difference ΔP between the upstream side and the downstream side of the mixing passage 30 is constant, the flow velocity of the mixed fluid M at the outlet opening 31 a of the mixing passage 30 increases as the pressure loss coefficient decreases. Therefore, the flow velocity V2 of the mixed fluid M of the second mixing passage 30B is lower than the flow velocity V1 of the mixed fluid M of the first mixing passage 30A. That is, the difference in flow velocity of the mixed fluid M flowing out of the first mixing passage 30A and the second mixing passage 30B becomes larger than that in a case in which the pressure loss coefficients of the mixing passages 30 are the same.

In this way, in this embodiment, the pressure loss coefficients of the flow paths of the mixing passages 30 are made different from each other so that the difference in flow velocity of the mixed fluid M flowing out of the mixing passages 30 becomes larger than that of a case in which the mixing passages 30 have the same flow path shape.

As a result, the variation in the outlet side flow velocity distribution D2 (see FIG. 6 ) of this embodiment that changes the pressure loss coefficient of each mixing passage 30 becomes larger than the variation in the outlet side flow velocity distribution D2 of the comparative example (see FIG. 5 ) in which each mixing passage 30 has the same shape.

Furthermore, as shown in FIG. 6 , in this embodiment, the variation in the outlet side flow velocity distribution D2 is larger than the variation in the inlet side flow velocity distribution D1.

In this way, since the outlet side flow velocity distribution D2 of the mixed fluid M is non-uniform, the position of the flame surface S formed by the flame of each mixing passage 30 also varies in the direction of the axis O. Therefore, it is possible to prevent the flame surface S from being aligned in the axial direction and to reduce combustion oscillation.

Further, since the flow path shape of the inlet portions 32 are made different among the mixing passages 30, design can be performed without adversely affecting combustion. That is, since a flam is formed on the side of the downstream end surface 22 of the mixing portion 20, a problem such as flashback and NOX will occur due to a change in the combustion state when the flow path shape on the outlet side of the mixing passage 30 is changed carelessly. On the other hand, in this embodiment, the above problem can be avoided by changing the shape on the side of the downstream end surface 22 of the mixing passage 30.

Further, since the inlet portion 32 has a bell mouth shape, the pressure loss coefficient of the flow path inside the mixing passage 30 can be kept low as a whole.

Second Embodiment

Next, a second embodiment will be described with reference to FIGS. 7 and 8 . In the second embodiment, components similar to those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

As shown in FIG. 7 , a plenum 35 which is a space is formed inside the mixing portion 20 of a combustor 50 of the second embodiment to avoid the region of the mixing passage 30. A fuel supply tube 51 which allows the plenum 35 to communicate with the fuel header 12 inside the end cover 11 is provided inside the plenum 35 along the axis O.

Then, as shown in FIG. 8 , a fuel injection hole 36 which allows the inside of the mixing passage 30 to communicate with the inside of the plenum 35 is formed on the inner peripheral surface of each mixing passage 30. The plurality of fuel injection holes 36 are formed at intervals in the circumferential direction of the mixing passage 30.

The fuel injection hole 36 functions as a fuel supply portion which supplies the fuel F into the mixing passage 30. The fuel F which is introduced from the fuel header 12 into the plenum 35 through the fuel supply tube 51 passes through the fuel injection hole 36 and is injected into the air A flowing through the mixing passage 30 to be mixed with the air. Accordingly, the mixed fluid M is generated.

Even in this embodiment, the pressure loss coefficients of the mixing passages 30 are different from each other as in the first embodiment. That is, in the second embodiment, the first mixing passage 30A in which the inlet portion 32 has a bell mouth shape and the second mixing passage 30B in which the inlet portion 32 has a straight tube shape similar to the main portion 31 are provided as the mixing passage 30.

Accordingly, the pressure loss coefficient of the first mixing passage 30A becomes smaller than the pressure loss coefficient of the second mixing passage 30B. That is, in the first mixing passage 30A, the air A is smoothly guided by the inlet portion 32 having a bell mouth shape, so that the effective cross-sectional area increases. On the other hand, in the second mixing passage 30B, the air A does not flow smoothly and the effective cross-sectional area decreases. As a result, the flow velocity of the mixed fluid M flowing out of the first mixing passage 30A becomes higher than the flow velocity of the mixed fluid M flowing out of the second mixing passage 30B.

In this way, even in this embodiment, the pressure loss coefficient of each mixing passage 30 is set so that the difference in flow velocity of the mixed fluid M flowing out of the mixing passages 30 increases compared to a case in which the mixing passages 30 have the same shape. Further, the variation in the outlet side flow velocity distribution D2 of the mixed fluid flowing out of each mixing passage 30 becomes larger than the variation in the inlet side flow velocity distribution D1 of the air A flowing into each mixing passage 30.

Therefore, it is possible to suppress the flame surface S from being aligned in the direction of the axis O and to reduce combustion oscillation as in the first embodiment.

Other Embodiments

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical idea of the invention.

For example, in the embodiment, the pressure loss coefficients of the mixing passages 30 are made different from each other by changing the outer diameter of the nozzle outer peripheral surface 43 of the fuel nozzle 40 or the shape of the inlet portion 32 of the mixing passage 30. However, the invention is not limited thereto and the pressure loss coefficients of the mixing passages 30 may be different from each other by adopting various configurations.

Both the shape of the nozzle outer peripheral surface 43 and the shape of the inlet portion 32 of the mixing passage 30 may be different among the mixing passages 30 by combining the first embodiment and the second embodiment.

In a combustor 60 of a modified example shown in FIG. 9 , the pressure loss coefficients of the mixing passages 30 (the first mixing passage 30A and the second mixing passage 30B) may be made different by changing the shape of the inlet portion 32 of each mixing passage 30 while maintaining the bell mouth shape for the inlet portion 32. For example, the inner diameter and the diameter expansion rate of the bell mouth shape may be changed or the length of the bell mouth in the direction of the axis O may be changed.

Appendix

The combustor 3 and the gas turbine 1 described in each embodiment are understood, for example, as below.

(1) The combustors 3, 50, and 60 according to a first aspect include: the mixing portion 20 which is provided with the plurality of mixing passages 30 passing through the mixing portion 20 so as to be extended from an upstream end surface 21 to a downstream end surface 22 of the mixing portion 20 intersecting an axis O of the combustor 3, air being introduced to the plurality of the mixing passages 30 from the upstream end surface 21 of the mixing portion 20; and a fuel supply portion which is configured to supply the air introduced to the mixing passages 30 with fuel F to generate mixed fluid M, wherein flow paths of the mixing passages 30 have different pressure loss coefficients so that the differences in the flow velocity of the mixed fluid M flowing through the mixing passages 30 at the downstream end surface 22 of the mixing portion 20 are greater those of a case where the mixing passages 30 have the same flow path shape.

Accordingly, the flame surface S formed by each mixing passage 30 on the side of the downstream end surface 22 is shifted in the direction of the axis O of the combustor 3. Accordingly, it is possible to suppress the combustion oscillation that occurs when the flame surfaces S of the mixing passages 30 are aligned in the direction of the axis O of the combustor 3.

(2) The combustors 3, 50, and 60 according to a second aspect are the combustors 3, 50, and 60 according to the first aspect, wherein each of the mixing passage 30 may include the inlet portion 32 which is continuous to the upstream end surface of the mixing portion 30 and the main portion 31 which is extended from the inlet portion 32 to the downstream end surface 22 of the mixing portion 20 and of which the inner diameter is constant throughout the entire of the main portion 31, and wherein the inlet portions 32 of the mixing passages 30 may have different flow path shapes.

Since a flame is formed on the side of the downstream end surface 22 of the mixing portion 20, a problem may occur due to a change in combustion state if the flow path shape on the outlet side of the mixing passage 30 is changed carelessly. In this aspect, since the flow path shape of the inlet portion 32 on the side of the upstream end surface 21 is changed instead of the side of the downstream end surface 22 of the mixing passage 30, the occurrence of the above problem can be avoided.

(3) The combustor 3 according to a third aspect is the combustor 3 according to the second aspect, wherein the fuel supply portion may have the fuel nozzles 40, tips 41 of which are inserted into the upstream end surface 21 of the mixing portion 20, supplying fuel F into the mixing passage 30 through the tips of the fuel nozzles, and wherein the tips 41 of the fuel nozzles 40 may have different outer diameters.

Accordingly, the flow path shapes of the inlet portions 32 of the plurality of mixing passages 30 can be made different.

(4) The combustor 3 according to a fourth aspect is the combustor 3 according to the third aspect, wherein each of the inlet portions 32 of the mixing passages 30 may have a bell mouth shape, in the inner diameter increases toward the upstream end surface 21 of the mixing portion 20.

Accordingly, the pressure loss coefficient of the flow path inside the mixing passage 30 can be kept low as a whole.

(5) The combustor 50 according to a fifth aspect is the combustor 50 according to the second aspect, wherein the fuel supply portions 36 and 40 may have the fuel injection holes 36 supplying the fuel F into the mixing passages 30 from surroundings of the mixing passages 30, and wherein the mixing portion 20 may have: the first mixing passage 30A in which the inlet portion 32 is continuous to the main portion 31, has a constant diameter and has a same inner diameter as the main portion 31, and the second mixing passage 30B in which the inlet portion 32 has a bell mouth shape in which in the inner diameter is increased toward the upstream end surface 21 of the mixing portion 20.

Accordingly, the flow velocity of the mixed fluid M from each mixing passage 30 can be made different while keeping a low pressure loss coefficient of the flow path inside the mixing passage 30 as a whole.

(6) The combustors 3, 50, and 60 according to a sixth aspect are the combustors 3, 50, and 60 according to any one of the first to fifth aspects, wherein the fuel supply portions 36 and 40 and the mixing passages 30 may be combined such that as the lower the pressure loss coefficient of the mixing passage 30, the higher the fuel supply rate of the fuel supply portion.

Accordingly, the fuel-air ratio of the mixed fluid M of each mixing passage 30 can be made uniform.

(7) A gas turbine 1 according to a seventh aspect includes: the compressor 2 which generates the air A; the combustors 3, 50, and 60 according to any one of the first to sixth aspects generating the combustion gas C by mixing the fuel F with the air A compressed by the compressor 2 and combusting the generated mixed fluid M; and the turbine 4 being driven by the combustion gas C.

EXPLANATION OF REFERENCES 1 Gas turbine 2 Compressor 3 Combustor 4 Turbine 10 Outer cylinder 11 End cover 12 Fuel header 13 Inner cylinder 20 Mixing portion 21 Upstream end surface 22 Downstream end surface 30 Mixing passage 30A First mixing passage 30B Second mixing passage 31 Main portion 31 a Outlet opening 32 Inlet portion 32 a Inlet opening 35 Plenum 36 Fuel injection hole 38 Support portion 40 Fuel nozzle 40A First nozzle 40B Second nozzle 41 Tip 42 Fuel flow path 42 a Tip opening 43 Nozzle outer peripheral surface 50 Combustor 51 Fuel supply tube 60 Combustor B1 First group B2 Second group R1 Inner peripheral system R2 Outer peripheral system D1 Inlet side flow velocity distribution D2 Outlet side flow velocity distribution S Flame surface A Air F Fuel M Mixed fluid C Combustion gas O Axis 

What is claimed is:
 1. A combustor comprising: a mixing portion which is provided with a plurality of mixing passages passing through the mixing portion so as to be extended from an upstream end surface to a downstream end surface of the mixing portion intersecting an axis of the combustor, air being introduced to the plurality of the mixing passages from the upstream end surface of the mixing portion; and a fuel supply portion which is configured to supply the air introduced to the mixing passages with fuel to generate mixed fluid, wherein flow paths of the mixing passages have different pressure loss coefficients so that the differences in the flow velocity of the mixed fluid flowing through the mixing passages at the downstream end surface of the mixing portion are greater than those of a case where the mixing passages have the same flow path shape.
 2. The combustor according to claim
 1. wherein each of the mixing passages includes: an inlet portion which is continuous to the upstream end surface of the mixing portion, and a main portion which is extended from the inlet portion to the downstream end surface of the mixing portion and of which an inner diameter is constant throughout the entire of the main portion, and wherein the inlet portions of the mixing passages have different flow path shapes.
 3. The combustor according to claim 2, wherein the fuel supply portion has fuel nozzles, tips of which are inserted into the mixing passages from the upstream end surface of the mixing portion, supplying fuel into the mixing passages through the tips of the fuel nozzles, and wherein the tips of the fuel nozzles have different outer diameters.
 4. The combustor according to claim
 3. wherein each of the inlet portions of the mixing passages has a bell mouth shape, an inner diameter increases toward the upstream end surface of the mixing portion.
 5. The combustor according to claim
 2. wherein the fuel supply portion has fuel injection holes supplying fuel into the mixing passages from surroundings of the mixing passages, and wherein the mixing portion includes: a first mixing passage in which the inlet portion is continuous to the main portion, has a constant inner diameter and has a same inner diameter as the main portion, and a second mixing passage in which the inlet portion has a bell mouth shape in which an inner diameter is increased toward the upstream end surface of the mixing portion.
 6. The combustor according to claim
 1. wherein the fuel supply portions and the mixing passages are combined such that the lower the pressure loss coefficient of the mixing passage, the higher the fuel supply rate of the fuel supply portion.
 7. A gas turbine comprising a compressor which generates air; the combustor according to claim 1 generating a combustion gas by mixing a fuel with air compressed by the compressor and combusting the generated mixed fluid; and a turbine being driven by the combustion gas. 